Industrial sensors are commonly used in a wide variety of applications and environments. Industrial sensors, such as proximity, mechanical switches, optical and photoelectric sensors, can be used to detect the presence or absence of targets on a conveyor belt, for example. Likewise, safety rated sensors can be used to prevent unauthorized or unintended access into a hazardous area, such as a safety interlock sensor that detects that a machinery guard door is closed before the machine operates. In addition, industrial sensors can be used to monitor various components of process machinery.
Industrial sensors often use one or more light sources that serve as indicators to convey a status signal, such as power, output, or margin, to an end user during set-up and operation. Light from the light source is often conveyed through a light pipe or similar optical structure serving to guide the light to the external environment. The light source is often colored or projected through a colored lens to emit colored light, often green, yellow, orange, or red. The visibility of these light-guide-coupled light sources is usually good when viewed head-on by the end-user. However, the visibility of these light-guide-coupled light sources is often poor when viewed from a large off-center angle, such as when viewed by the end-user from the side. The visibility of these light sources is often reduced as the distance to the exterior environment increases.
Various solutions have been tried to address poor sensor indicator visibility from viewing angles other than head-on, such as selecting brighter (and possibly larger) light source components, increasing the electrical current supplied to the light source, moving the light source closer to the exterior surface, and using physical optical structures such as prisms, or light pipes. Although these methods can increase indicator visibility from directions other than head-on, they include various drawbacks, such as more expensive parts, additional part processing, increased electric load on a base circuit, presenting dirt traps that reduce product hygiene, and increased housing size to accommodate larger parts or additional structures.
What is needed is a device or method that preserves the head-on visibility of sensor indicators while simultaneously enhancing the visibility from viewing angles other than head-on, and overcomes the above-discussed drawbacks.